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Antivirus companies say they have cracked an algorithm that was being used by the Sober worm to “communicate” with its author.The latest variant of the Sober worm caused havoc in November by duping users into executing it by masking itself as e-mails from the FBI and CIA. Antivirus companies were aware that the worm somehow knew how to update itself via the Web. The worm’s author programmed this functionality to control infected machines and, if required, change their behavior.